My husband tried Ensure, then Isomil and found Nestle's Pro Balance settled best in his stomach. Also, he put whole milk with either chocolate or strawberry syrup in the feeding bag, alternating with the Pro Balance. After ingesting the liquid supplements, flushing the feeding tube with 1/2 to 1 liter of water, on a very slow drip, helped his digestion. I don't know if your father in law is using a piston syringe, electric pump or a gravity bag for his tube feedings, but my husband found that a gravity bag on an i.v. pole with a very, very slow drip kept him from getting nauseous. Hope this helps. God Speed!
Victrola